Use-dependent plasticity of the human motor cortex in health and disease.

The adult brain can reorganize to accommodate environmental modifications and to compensate for lost function, a process known as plasticity. The last few years have provided extraordinary evidence regarding the mechanisms underlying plastic changes and have spurred the development of new strategies to modulate these processes. The ability of the mature brain to constantly reorganize has gained further credibility with the advent of transcranial magnetic stimulation (TMS). Plasticity is thought to be influenced by neurotransmitters and decreases substantially with normal aging. TMS has demonstrated that remarkable plastic changes occur in response to pharmacological agents and peripheral or central nervous system injury. Plastic changes are also associated with intense motor training such as constraint-induced therapy (CIT). For instance, premedication with amphetamine resulted in faster induction, increased magnitude, and prolonged duration of plasticity elicited by motor training compared to a placebo. Similarly, peripheral sensory stimulation resulted in enhancement of plastic changes. Finally, TMS cortical motor maps enlarge after CIT in stroke patients. This work discusses the potential of TMS as a useful tool to probe novel strategies to enhance plasticity in humans.     

Compensation strategy of matrix converter fed induction motor drive under input voltage and load disturbances using internal model control

The Matrix Converter (MC) is well known for its diverse advantages and applications but the output characteristics are adversely affected by the input voltage disturbances because there is no energy storage elements present in the dc link. Hence the matrix converter fed drive performance is affected. In this paper, Internal Model Control (IMC) based controller which is capable of achieving perfect set point tracking and disturbance rejection is proposed for compensating the voltage disturbances and load disturbances of matrix converter fed vector controlled Induction Motor (IM) drives. Modeling of matrix converter with input voltage disturbances and parameter estimation of IMC based speed and current controllers for vector controlled induction motor drive are described in this paper. The simulation results validate the input voltage disturbance rejection and improved dynamic performance of matrix converter fed induction motor drive obtained using IMC based controller.     

DC/AC three phase converter with resonant circuit at the input and intermediate RF circuit for supplying a three phase asynchronous motor

Contents This paper presents a dc/ac three phase converter aimed to supply an asynchronous three phase motor with variable voltage and frequency. Equipping the input with a resonant circuit, the switching loss in the semiconductor devices is reduced and the EMO problem is less severe because the resonant voltage pulses have a lower dv/dt.

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Ein Umrichter mit Resonanzkreis am Eingang und RF-Zwischenkreis zur Speisung eines Drehstrom-Asynchronmotors

Übersicht In der Arbeit wird ein Umrichter zur Speisung eines Drehstrom-Asynchronmotors mit variabler Spannung und Frequenz vorgestellt. Dadurch, daß am Eingang ein Resonanzkreis vorgesehen ist, werden die Schaltverluste in den Halbleiterkomponenten des Umrichters reduziert. Die Probleme durch die elektromagnetische Störabstrahlung nehmen ab, da die Resonanzpulse kleinere Steigungen dv/dt haben.

     

Nerve cuff recordings of muscle afferent activity from tibial and peroneal nerves in rabbit during passive ankle motion.

Activity from muscle afferents regarding ankle kinesthesia was recorded using cuff electrodes in a rabbit preparation in which tactile input from the foot was eliminated. The purpose was to determine if such activity can provide information useful in controlling functional electrical stimulation (FES) systems that restore mobility in spinal injured man. The rabbit's ankle was passively flexed and extended while the activity of the tibial and peroneal nerves was recorded. Responses to trapezoidal stimulus profiles were investigated for excursions from 10 degrees to 60 degrees using velocities from 5 degrees/s to 30 degrees/s and different initial ankle positions. The recorded signals mainly reflect activity from primary and secondary muscle afferents. Dorsiflexion stretched the ankle extensors and produced velocity dependent activity in the tibial nerve, and this diminished to a tonic level during the stimulus plateau. The peroneal nerve was silent during dorsiflexion, but was activated by stretch of the peroneal muscles during ankle extension. The responses of the two nerves behaved in a reciprocal manner, but exhibited considerable hysteresis, since motion that relaxed the stretch to the driving muscle produced an immediate cessation of the prior stretch induced activity. A noted difference between the tibial and peroneal nerve responses is that the range of joint position change that activated the flexor afferents was greater then for the extensor afferents. Ankle rotation at higher velocities increased the dynamic stretch evoked responses during the stimulus ramp but showed no effect on the tonic activity during the stimulus plateau. Prestretching the muscles by altering the initial position increased the response to the ramp movement, however, for the peroneal nerve, when the prestretch brought the flexor muscles near to their maximal lengths, the response to additional stretch provided by the ramp movement was diminished. The results indicate that the whole nerve recorded muscle afferent activity may be useful for control of FES assisted standing, because it can indicate the direction of rotation of the passively moved ankle joint, along with coarse information regarding the rate of movement and static joint position.     

Relaxing the maximum dc input amplitude vs. consumption trade‐off in differential‐input band‐pass biquad filters

This paper shows that an important part of the power consumption of a biquad band‐pass filter is associated with the feedback loop that fixes the high‐pass frequency and blocks the direct current (dc) input signals. The dc input amplitude that can be blocked is related to the maximum output current that one of the transconductors can provide, hence impacting on the required consumption through this effect. Then, a technique that efficiently blocks the dc input signal and fixes the high‐pass frequency is introduced and analyzed in depth. Moreover, an architecture for ultra‐low‐power differential‐input biquads is fully presented. The proposed architecture enables lowering the power consumption or blocking higher levels of dc input without jeopardizing the power consumption. Results show that the proposed architecture, compared with a traditional one, presents a 30% reduction in power consumption and more than doubles the dc input that can be blocked. Copyright © 2016 John Wiley & Sons, Ltd.     

能馈电子负载中低压大电流输入高增益变换器设计

针对能馈电子负载低压大电流输入、输入电流纹波小和高增益的要求,论文给出了两级DC/DC升压的boost级联拓扑方案,第一级的交错并联boost电路满足大电流输入的同时减小了输入电流纹波,两级boost级联的拓扑可以方便地实现高升压比。文中分析了电路的运行原理和电路特性,给出了输入电流闭环的设计过程,并利用DSP实现了输...     

Considerations on the thrust‐to‐input ratio of a cylindrical moving‐coil‐type linear dc motor

Linear dc motors (LDMs) are widely used for servo‐actuators, compressors, and so on. High‐efficiency LDMs are strongly desired for compressors. To realize LDMs with high‐efficiency characteristics, decreasing the copper losses, namely, thrust‐to‐input ratio, F/P, must be increased. This paper describes an optimization method for the F/P of a moving‐coil‐type LDM. The following results are obtained:

• 1 Simplified expression for the F/P of the LDM is derived from the permeance analysis method. The effects of dimensions of the LDM on the F/P of the LDM are investigated through the simplified expression for the F/P. As a result, the optimum dimension of the LDM for maximizing the F/P exists.
• 2 When the static thrust is 100 N, the measured F/P of the initial LDM is 7.9 N/W, and the errors using the simplified expression for the F/P and the finite element method (FEM) are 33 and 8%, respectively. Derived simplified expression for the F/P is useful because the F/P can be calculated easily.
• 3 An improved LDM, which has 26% higher F/P than those of the initial LDM, is designed by using the permeance analysis method and the FEM. © 2000 Scripta Technica, Electr Eng Jpn, 131(1): 103–111, 2000

     

Feature detection in motor cortical spikes by principal component analysis.

Principal component analysis was performed on recorded neural spike trains in rats' motor cortices when rats were involved in real-time control tasks using brain-machine interfaces. The rat with implanted microelectrode array was placed in a conditioning chamber, but freely moving, to decide which one of the two paddles should be activated to shift the cue light to the center. It is found that the principal component feature vectors revealed the importance of individual neurons and windows of time in the decision making process. In addition, one of the first principal components has much higher discriminative capability than others, although it represents only a small percentage of the total variance in the data. Using one to six principal components with a Bayes classifier achieved classification accuracy comparable to that obtained by a more sophisticated high performance support vector classifier.     

第一讲电涌保护的作用

从现代防雷工程的发展和雷害事故的统计说明建筑物内电气电子系统电涌保护的需要,然后阐明了现代防雷体系中电涌保护限制雷电电涌和操作电涌的作用.     

Local field potential spectral tuning in motor cortex during reaching.

In this paper, intracortical local field potentials (LFPs) and single units were recorded from the motor cortices of monkeys (Macaca fascicularis) while they preformed a standard three-dimensional (3-D) center-out reaching task. During the center-out task, the subjects held their hands at the location of a central target and then reached to one of eight peripheral targets forming the corners of a virtual cube. The spectral amplitudes of the recorded LFPs were calculated, with the high-frequency LFP (HF-LFP) defined as the average spectral amplitude change from baseline from 60 to 200 Hz. A 3-D linear regression across the eight center-out targets revealed that approximately 6% of the beta LFPs (18-26 Hz) and 18% of the HF-LFPs were tuned for velocity (p-value < 0.05), while 10% of the beta LFPs and 15% of the HF-LFPs were tuned for position. These results suggest that a multidegree-of-freedom brain-machine interface is possible using high-frequency LFP recordings in motor cortex.     

数字量输入式合并单元的白噪声处理

为了提高数字化采样的可靠性及精确度,白噪声问题一直是工业界和学术界的研究热点。首先,结合智能变电站的应用实例,给出了电子式互感器的输出波形,并对白噪声分量进行频谱分析。进而,考虑滤波效果、算法稳定性、延时时间等因素,设计了相应的数字滤波器,并给出了滤波参数及处理结果。最后,结合非周期分量衰减时间常数、最大峰值瞬时误差等指标,分析和评估了滤波算法对暂态性能的影响。分析结果表明,数字滤波算法可以使白噪声削弱一半以上,且不会影响暂态性能。     

MMC-UPQC在RTDS仿真中的脉冲输入方案设计

统一电能质量控制器（UPQC）装置投入现场运行之前,开展基于实时数字仿真器（RTDS）的实验是非常重要的一步,不仅能够使UPQC控制器的功能和性能得到较为充分的验证,还可以积累经验为后续的物理实验提供重要的指导和借鉴。基于模块化多电平换流器（MMC）结构的UPQC由于模块数较多,需要触发的IGBT很多,为了合理利用RTDS宝贵的资源,在开展RTDS实验的时候,必须要对资源分配进行优化设计,其中脉冲的输入方案就是其中的一个重要环节。论文在分析说明MMC-UPQC的拓扑结构的基础之上,首先对RTDS及UPQC的物理控制器的结构和需求进行了梳理和分析,然后给出了两种脉冲输入方案并进行了对比分析,最后在RTDS平台上进行了数字-物理闭环仿真实验,实验结果验证了所给脉冲编码方案的可行性。